GR6 OE Style Sump Filter
Video of how to change the filter yourself:
More info:
This is a data log of what a clogged line filter looks like. Note how line pressure (ORANGE LINE) drops off and can't keep up with target (BLUE LINE) at low pressure conditions:
Here is another data log of the same unit with the line filter replaced. Note how line pressure (ORANGE LINE) follows target (BLUE LINE) perfectly: